"Your first day in the prison yard," he said to a colleague, "you've got to punch the biggest guy out or else they're going to keep doing it to you."

The analogy from the aspiring mayor of New York, overheard by a reporter, revealed much about congressional Democrats' thinking as they stew over President Obama's tax-cut deal with Republicans. They know they have little chance of blocking the compromise, which preserves low rates for millionaires. Their protest, then, amounts to an exercise in venting -- coupled with a hope that Obama will think twice before triangulating against congressional Democrats the next time. Call it the lame duck that roared.

As was the case with the public-option protest during the health-care fight, the liberals' screaming and yelling is, at least so far, only noise. If that's the best they've got -- and that's with House Democrats still in the majority -- Obama could justifiably conclude that he ought to triangulate more often.

On Tuesday, the rebellious Democrats gave the impression they could mount a serious fight. Sen. Bernie Sanders (I-Vt.) said Obama had signed on to a "morally bankrupt" and "reprehensible" policy. Sen. Mary Landrieu (D-La.) said the deal approached "moral corruptness." Others spoke about getting "screwed" and "taken to the cleaners."

But the angry words were little more than what Republican Sen. Jon Kyl (Ariz.) had derisively referred to last week as "a political catharsis on the Democratic side."

By Wednesday evening, even some Democrats had embraced that theme. "This is a little catharsis going on in there," said Rep. Sam Farr (D-Calif.), midway through Biden's two-hour pummeling in the Capitol basement. "The president's on the defense, the vice president's on the defense."

The administration fought back with a campaign-style persuasion effort. White House officials distributed to each of the Democratic lawmakers a bar graph labeled "What WE Got" and "What THEY Got." (According to the graph, "we" got more than "they.")

The average insurgency, the foreign policy experts say, lasts about ten years. The average liberal rebellion against Obama appears to last about a day. The crumbling began early in the day Wednesday, when Sen. Jim Webb (D-Va.) issued a statement calling the tax deal "the ultimate stimulus plan."

On Tuesday, Senate Majority Leader Harry Reid would only say of the compromise: "I'm going to do what I think is right when it all comes down to it." But on Wednesday, after a lengthy session with administration officials Gene Sperling and Jack Lew, Reid told reporters that "they did some explanations I think were helpful to the caucus."

Sen. Kent Conrad, the budget committee chairman, said the closed-door session had changed "the tenor of the discussion" to a "more positive" vibe. And Sen. Joe Lieberman (I-Conn.) forecast with confidence: "In the end there will be enough Democratic votes in the Senate to join with Republicans to pass this bill."